Coffee is a beverage which is brewed by extracting water soluble flavor and aroma components from roasted coffee beans. The essential flavor and aroma component in coffee is caffeol, an oil that is partially soluble in water. Thus coffee extract is principally a caffeol-water emulsion containing minor amounts of other flavor and aroma components. Because roasted coffee beans have a rigid structure, they are usually milled or ground to form coffee grounds typically ranging in size from about 30 to 200 mesh (U.S.A. sieve series). This substantially increases the surface area of the coffee grounds available for extraction.
Various apparatuses are known for automatically brewing coffee. One type of coffee brewing apparatus is a drip type coffee maker in which preheated water filters through coffee grounds by gravity. In the drip type coffee maker, water preheated to just below its boiling point is introduced at the top of a static bed consisting of coffee grounds and flows through the static bed by the force of gravity. The forces exerted on the static bed by gravity and the water compact the bed leading to water channelling through and uneven wetting of the static bed. This in turn results in uneven and incomplete extraction of caffeol from the coffee grounds.
Another type of coffee brewing apparatus is a percolation type coffee maker. In the percolation type coffee maker, boiling water or steam is repeatedly passed through a quantity of coffee grounds for a predetermined time period. However, a major disadvantage of repeatedly passing water through the coffee grounds is that an undesirable or less than optimum taste develops in the coffee extract.
Still another type of coffee brewing apparatus confines the coffee grounds in a rotating housing and uses centrifugal force to filter preheated water through coffee grounds. For example, U.S. Pat. No. 3,967,546 to Cailliot describes a coffee brewing apparatus in which a bottom retractable disc and an upper retractable cone form a rotatable holder driven by a gear mechanism for a coffee grounds-liquid mixture. A 0.2 mm gap between the disc and the cone acts as a filter to separate the liquid from the coffee grounds. When the rotation stops, the bottom retractable disc disengages from the cone allowing the coffee grounds to be removed from the cone.
U.S. Pat. Nos. 4,473,002 and 4,464,982 to Leuscher describe a centrifugal type coffee brewing apparatus having a receptacle for holding coffee grounds. When the receptacle is rotated, water is transferred from a water container directly below the coffee grounds receptacle upward and into the ground coffee receptacle. The coffee grounds receptacle contains a slot in its upper portion which serves to separate the liquid from the coffee grounds.
U.S. Pat. No. 3,233,535 to Fowlie also describes a centrifugal type coffee brewing apparatus in which hot water is fed into the upper portion of a brewing case containing coffee grounds before centrifugal rotation of the brewing case begins. The feeding of hot water into the upper portion of a brewing chamber containing coffee grounds before centrifugal rotation of the brewing chamber at 5,000 rpm also is described in U.S. Pat. No. 4,962,693 to Miwa et al.
However, prior to the present invention, rotating or centrifugal type coffee makers, did not produce coffee having the proper amount of flavor and aroma components due to a failure to wet all surfaces of the coffee grounds or failure to drive the water into the coffee grounds, and/or failure to selectively extract caffeol from an aqueous solution containing coffee grounds.
There exists, therefore, the need for an apparatus and a method for brewing coffee which do not exhibit the above-mentioned disadvantages, as well as other disadvantages inherent therein. The present invention fulfills this need.